src/librustc/middle/expr_use_visitor.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A different sort of visitor for walking fn bodies.  Unlike the
  12 //! normal visitor, which just walks the entire body in one shot, the
  13 //! `ExprUseVisitor` determines how expressions are being used.
  14
  15 pub use self::MutateMode::*;
  16 pub use self::LoanCause::*;
  17 pub use self::ConsumeMode::*;
  18 pub use self::MoveReason::*;
  19 pub use self::MatchMode::*;
  20 use self::TrackMatchMode::*;
  21 use self::OverloadedCallType::*;
  22
  23 use middle::{def, region, pat_util};
  24 use middle::mem_categorization as mc;
  25 use middle::mem_categorization::Typer;
  26 use middle::ty::{self};
  27 use middle::ty::{MethodCall, MethodObject, MethodTraitObject};
  28 use middle::ty::{MethodOrigin, MethodParam, MethodTypeParam};
  29 use middle::ty::{MethodStatic, MethodStaticUnboxedClosure};
  30 use util::ppaux::Repr;
  31
  32 use std::marker;
  33 use syntax::{ast, ast_util};
  34 use syntax::ptr::P;
  35 use syntax::codemap::Span;
  36
  37 ///////////////////////////////////////////////////////////////////////////
  38 // The Delegate trait
  39
  40 /// This trait defines the callbacks you can expect to receive when
  41 /// employing the ExprUseVisitor.
  42 pub trait Delegate<'tcx> {
  43     // The value found at `cmt` is either copied or moved, depending
  44     // on mode.
  45     fn consume(&mut self,
  46                consume_id: ast::NodeId,
  47                consume_span: Span,
  48                cmt: mc::cmt<'tcx>,
  49                mode: ConsumeMode);
  50
  51     // The value found at `cmt` has been determined to match the
  52     // pattern binding `matched_pat`, and its subparts are being
  53     // copied or moved depending on `mode`.  Note that `matched_pat`
  54     // is called on all variant/structs in the pattern (i.e., the
  55     // interior nodes of the pattern's tree structure) while
  56     // consume_pat is called on the binding identifiers in the pattern
  57     // (which are leaves of the pattern's tree structure).
  58     //
  59     // Note that variants/structs and identifiers are disjoint; thus
  60     // `matched_pat` and `consume_pat` are never both called on the
  61     // same input pattern structure (though of `consume_pat` can be
  62     // called on a subpart of an input passed to `matched_pat).
  63     fn matched_pat(&mut self,
  64                    matched_pat: &ast::Pat,
  65                    cmt: mc::cmt<'tcx>,
  66                    mode: MatchMode);
  67
  68     // The value found at `cmt` is either copied or moved via the
  69     // pattern binding `consume_pat`, depending on mode.
  70     fn consume_pat(&mut self,
  71                    consume_pat: &ast::Pat,
  72                    cmt: mc::cmt<'tcx>,
  73                    mode: ConsumeMode);
  74
  75     // The value found at `borrow` is being borrowed at the point
  76     // `borrow_id` for the region `loan_region` with kind `bk`.
  77     fn borrow(&mut self,
  78               borrow_id: ast::NodeId,
  79               borrow_span: Span,
  80               cmt: mc::cmt<'tcx>,
  81               loan_region: ty::Region,
  82               bk: ty::BorrowKind,
  83               loan_cause: LoanCause);
  84
  85     // The local variable `id` is declared but not initialized.
  86     fn decl_without_init(&mut self,
  87                          id: ast::NodeId,
  88                          span: Span);
  89
  90     // The path at `cmt` is being assigned to.
  91     fn mutate(&mut self,
  92               assignment_id: ast::NodeId,
  93               assignment_span: Span,
  94               assignee_cmt: mc::cmt<'tcx>,
  95               mode: MutateMode);
  96 }
  97
  98 #[derive(Copy, PartialEq, Show)]
  99 pub enum LoanCause {
 100     ClosureCapture(Span),
 101     AddrOf,
 102     AutoRef,
 103     RefBinding,
 104     OverloadedOperator,
 105     ClosureInvocation,
 106     ForLoop,
 107     MatchDiscriminant
 108 }
 109
 110 #[derive(Copy, PartialEq, Show)]
 111 pub enum ConsumeMode {
 112     Copy,                // reference to x where x has a type that copies
 113     Move(MoveReason),    // reference to x where x has a type that moves
 114 }
 115
 116 #[derive(Copy, PartialEq, Show)]
 117 pub enum MoveReason {
 118     DirectRefMove,
 119     PatBindingMove,
 120     CaptureMove,
 121 }
 122
 123 #[derive(Copy, PartialEq, Show)]
 124 pub enum MatchMode {
 125     NonBindingMatch,
 126     BorrowingMatch,
 127     CopyingMatch,
 128     MovingMatch,
 129 }
 130
 131 #[derive(PartialEq,Show)]
 132 enum TrackMatchMode<T> {
 133     Unknown,
 134     Definite(MatchMode),
 135     Conflicting,
 136 }
 137
 138 impl<T> marker::Copy for TrackMatchMode<T> {}
 139
 140 impl<T> TrackMatchMode<T> {
 141     // Builds up the whole match mode for a pattern from its constituent
 142     // parts.  The lattice looks like this:
 143     //
 144     //          Conflicting
 145     //            /     \
 146     //           /       \
 147     //      Borrowing   Moving
 148     //           \       /
 149     //            \     /
 150     //            Copying
 151     //               |
 152     //          NonBinding
 153     //               |
 154     //            Unknown
 155     //
 156     // examples:
 157     //
 158     // * `(_, some_int)` pattern is Copying, since
 159     //   NonBinding + Copying => Copying
 160     //
 161     // * `(some_int, some_box)` pattern is Moving, since
 162     //   Copying + Moving => Moving
 163     //
 164     // * `(ref x, some_box)` pattern is Conflicting, since
 165     //   Borrowing + Moving => Conflicting
 166     //
 167     // Note that the `Unknown` and `Conflicting` states are
 168     // represented separately from the other more interesting
 169     // `Definite` states, which simplifies logic here somewhat.
 170     fn lub(&mut self, mode: MatchMode) {
 171         *self = match (*self, mode) {
 172             // Note that clause order below is very significant.
 173             (Unknown, new) => Definite(new),
 174             (Definite(old), new) if old == new => Definite(old),
 175
 176             (Definite(old), NonBindingMatch) => Definite(old),
 177             (Definite(NonBindingMatch), new) => Definite(new),
 178
 179             (Definite(old), CopyingMatch) => Definite(old),
 180             (Definite(CopyingMatch), new) => Definite(new),
 181
 182             (Definite(_), _) => Conflicting,
 183             (Conflicting, _) => *self,
 184         };
 185     }
 186
 187     fn match_mode(&self) -> MatchMode {
 188         match *self {
 189             Unknown => NonBindingMatch,
 190             Definite(mode) => mode,
 191             Conflicting => {
 192                 // Conservatively return MovingMatch to let the
 193                 // compiler continue to make progress.
 194                 MovingMatch
 195             }
 196         }
 197     }
 198 }
 199
 200 #[derive(Copy, PartialEq, Show)]
 201 pub enum MutateMode {
 202     Init,
 203     JustWrite,    // x = y
 204     WriteAndRead, // x += y
 205 }
 206
 207 #[derive(Copy)]
 208 enum OverloadedCallType {
 209     FnOverloadedCall,
 210     FnMutOverloadedCall,
 211     FnOnceOverloadedCall,
 212 }
 213
 214 impl OverloadedCallType {
 215     fn from_trait_id(tcx: &ty::ctxt, trait_id: ast::DefId)
 216                      -> OverloadedCallType {
 217         for &(maybe_function_trait, overloaded_call_type) in [
 218             (tcx.lang_items.fn_once_trait(), FnOnceOverloadedCall),
 219             (tcx.lang_items.fn_mut_trait(), FnMutOverloadedCall),
 220             (tcx.lang_items.fn_trait(), FnOverloadedCall)
 221         ].iter() {
 222             match maybe_function_trait {
 223                 Some(function_trait) if function_trait == trait_id => {
 224                     return overloaded_call_type
 225                 }
 226                 _ => continue,
 227             }
 228         }
 229
 230         tcx.sess.bug("overloaded call didn't map to known function trait")
 231     }
 232
 233     fn from_method_id(tcx: &ty::ctxt, method_id: ast::DefId)
 234                       -> OverloadedCallType {
 235         let method_descriptor = match ty::impl_or_trait_item(tcx, method_id) {
 236             ty::MethodTraitItem(ref method_descriptor) => {
 237                 (*method_descriptor).clone()
 238             }
 239             ty::TypeTraitItem(_) => {
 240                 tcx.sess.bug("overloaded call method wasn't in method map")
 241             }
 242         };
 243         let impl_id = match method_descriptor.container {
 244             ty::TraitContainer(_) => {
 245                 tcx.sess.bug("statically resolved overloaded call method \
 246                               belonged to a trait?!")
 247             }
 248             ty::ImplContainer(impl_id) => impl_id,
 249         };
 250         let trait_ref = match ty::impl_trait_ref(tcx, impl_id) {
 251             None => {
 252                 tcx.sess.bug("statically resolved overloaded call impl \
 253                               didn't implement a trait?!")
 254             }
 255             Some(ref trait_ref) => (*trait_ref).clone(),
 256         };
 257         OverloadedCallType::from_trait_id(tcx, trait_ref.def_id)
 258     }
 259
 260     fn from_unboxed_closure(tcx: &ty::ctxt, closure_did: ast::DefId)
 261                             -> OverloadedCallType {
 262         let trait_did =
 263             tcx.unboxed_closures
 264                .borrow()
 265                .get(&closure_did)
 266                .expect("OverloadedCallType::from_unboxed_closure: didn't \
 267                         find closure id")
 268                .kind
 269                .trait_did(tcx);
 270         OverloadedCallType::from_trait_id(tcx, trait_did)
 271     }
 272
 273     fn from_method_origin(tcx: &ty::ctxt, origin: &MethodOrigin)
 274                           -> OverloadedCallType {
 275         match *origin {
 276             MethodStatic(def_id) => {
 277                 OverloadedCallType::from_method_id(tcx, def_id)
 278             }
 279             MethodStaticUnboxedClosure(def_id) => {
 280                 OverloadedCallType::from_unboxed_closure(tcx, def_id)
 281             }
 282             MethodTypeParam(MethodParam { ref trait_ref, .. }) |
 283             MethodTraitObject(MethodObject { ref trait_ref, .. }) => {
 284                 OverloadedCallType::from_trait_id(tcx, trait_ref.def_id)
 285             }
 286         }
 287     }
 288 }
 289
 290 ///////////////////////////////////////////////////////////////////////////
 291 // The ExprUseVisitor type
 292 //
 293 // This is the code that actually walks the tree. Like
 294 // mem_categorization, it requires a TYPER, which is a type that
 295 // supplies types from the tree. After type checking is complete, you
 296 // can just use the tcx as the typer.
 297
 298 pub struct ExprUseVisitor<'d,'t,'tcx:'t,TYPER:'t> {
 299     typer: &'t TYPER,
 300     mc: mc::MemCategorizationContext<'t,TYPER>,
 301     delegate: &'d mut (Delegate<'tcx>+'d),
 302 }
 303
 304 // If the TYPER results in an error, it's because the type check
 305 // failed (or will fail, when the error is uncovered and reported
 306 // during writeback). In this case, we just ignore this part of the
 307 // code.
 308 //
 309 // Note that this macro appears similar to try!(), but, unlike try!(),
 310 // it does not propagate the error.
 311 macro_rules! return_if_err {
 312     ($inp: expr) => (
 313         match $inp {
 314             Ok(v) => v,
 315             Err(()) => return
 316         }
 317     )
 318 }
 319
 320 /// Whether the elements of an overloaded operation are passed by value or by reference
 321 enum PassArgs {
 322     ByValue,
 323     ByRef,
 324 }
 325
 326 impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
 327     pub fn new(delegate: &'d mut Delegate<'tcx>,
 328                typer: &'t TYPER)
 329                -> ExprUseVisitor<'d,'t,'tcx,TYPER> {
 330         ExprUseVisitor {
 331             typer: typer,
 332             mc: mc::MemCategorizationContext::new(typer),
 333             delegate: delegate,
 334         }
 335     }
 336
 337     pub fn walk_fn(&mut self,
 338                    decl: &ast::FnDecl,
 339                    body: &ast::Block) {
 340         self.walk_arg_patterns(decl, body);
 341         self.walk_block(body);
 342     }
 343
 344     fn walk_arg_patterns(&mut self,
 345                          decl: &ast::FnDecl,
 346                          body: &ast::Block) {
 347         for arg in decl.inputs.iter() {
 348             let arg_ty = return_if_err!(self.typer.node_ty(arg.pat.id));
 349
 350             let fn_body_scope = region::CodeExtent::from_node_id(body.id);
 351             let arg_cmt = self.mc.cat_rvalue(
 352                 arg.id,
 353                 arg.pat.span,
 354                 ty::ReScope(fn_body_scope), // Args live only as long as the fn body.
 355                 arg_ty);
 356
 357             self.walk_irrefutable_pat(arg_cmt, &*arg.pat);
 358         }
 359     }
 360
 361     fn tcx(&self) -> &'t ty::ctxt<'tcx> {
 362         self.typer.tcx()
 363     }
 364
 365     fn delegate_consume(&mut self,
 366                         consume_id: ast::NodeId,
 367                         consume_span: Span,
 368                         cmt: mc::cmt<'tcx>) {
 369         let mode = copy_or_move(self.typer, &cmt, DirectRefMove);
 370         self.delegate.consume(consume_id, consume_span, cmt, mode);
 371     }
 372
 373     fn consume_exprs(&mut self, exprs: &Vec<P<ast::Expr>>) {
 374         for expr in exprs.iter() {
 375             self.consume_expr(&**expr);
 376         }
 377     }
 378
 379     pub fn consume_expr(&mut self, expr: &ast::Expr) {
 380         debug!("consume_expr(expr={})", expr.repr(self.tcx()));
 381
 382         let cmt = return_if_err!(self.mc.cat_expr(expr));
 383         self.delegate_consume(expr.id, expr.span, cmt);
 384         self.walk_expr(expr);
 385     }
 386
 387     fn mutate_expr(&mut self,
 388                    assignment_expr: &ast::Expr,
 389                    expr: &ast::Expr,
 390                    mode: MutateMode) {
 391         let cmt = return_if_err!(self.mc.cat_expr(expr));
 392         self.delegate.mutate(assignment_expr.id, assignment_expr.span, cmt, mode);
 393         self.walk_expr(expr);
 394     }
 395
 396     fn borrow_expr(&mut self,
 397                    expr: &ast::Expr,
 398                    r: ty::Region,
 399                    bk: ty::BorrowKind,
 400                    cause: LoanCause) {
 401         debug!("borrow_expr(expr={}, r={}, bk={})",
 402                expr.repr(self.tcx()), r.repr(self.tcx()), bk.repr(self.tcx()));
 403
 404         let cmt = return_if_err!(self.mc.cat_expr(expr));
 405         self.delegate.borrow(expr.id, expr.span, cmt, r, bk, cause);
 406
 407         // Note: Unlike consume, we can ignore ExprParen. cat_expr
 408         // already skips over them, and walk will uncover any
 409         // attachments or whatever.
 410         self.walk_expr(expr)
 411     }
 412
 413     fn select_from_expr(&mut self, expr: &ast::Expr) {
 414         self.walk_expr(expr)
 415     }
 416
 417     pub fn walk_expr(&mut self, expr: &ast::Expr) {
 418         debug!("walk_expr(expr={})", expr.repr(self.tcx()));
 419
 420         self.walk_adjustment(expr);
 421
 422         match expr.node {
 423             ast::ExprParen(ref subexpr) => {
 424                 self.walk_expr(&**subexpr)
 425             }
 426
 427             ast::ExprPath(..) => { }
 428
 429             ast::ExprUnary(ast::UnDeref, ref base) => {      // *base
 430                 if !self.walk_overloaded_operator(expr, &**base, Vec::new(), PassArgs::ByRef) {
 431                     self.select_from_expr(&**base);
 432                 }
 433             }
 434
 435             ast::ExprField(ref base, _) => {         // base.f
 436                 self.select_from_expr(&**base);
 437             }
 438
 439             ast::ExprTupField(ref base, _) => {         // base.<n>
 440                 self.select_from_expr(&**base);
 441             }
 442
 443             ast::ExprIndex(ref lhs, ref rhs) => {       // lhs[rhs]
 444                 if !self.walk_overloaded_operator(expr,
 445                                                   &**lhs,
 446                                                   vec![&**rhs],
 447                                                   PassArgs::ByRef) {
 448                     self.select_from_expr(&**lhs);
 449                     self.consume_expr(&**rhs);
 450                 }
 451             }
 452
 453             ast::ExprRange(ref start, ref end) => {
 454                 start.as_ref().map(|e| self.consume_expr(&**e));
 455                 end.as_ref().map(|e| self.consume_expr(&**e));
 456             }
 457
 458             ast::ExprCall(ref callee, ref args) => {    // callee(args)
 459                 self.walk_callee(expr, &**callee);
 460                 self.consume_exprs(args);
 461             }
 462
 463             ast::ExprMethodCall(_, _, ref args) => { // callee.m(args)
 464                 self.consume_exprs(args);
 465             }
 466
 467             ast::ExprStruct(_, ref fields, ref opt_with) => {
 468                 self.walk_struct_expr(expr, fields, opt_with);
 469             }
 470
 471             ast::ExprTup(ref exprs) => {
 472                 self.consume_exprs(exprs);
 473             }
 474
 475             ast::ExprIf(ref cond_expr, ref then_blk, ref opt_else_expr) => {
 476                 self.consume_expr(&**cond_expr);
 477                 self.walk_block(&**then_blk);
 478                 for else_expr in opt_else_expr.iter() {
 479                     self.consume_expr(&**else_expr);
 480                 }
 481             }
 482
 483             ast::ExprIfLet(..) => {
 484                 self.tcx().sess.span_bug(expr.span, "non-desugared ExprIfLet");
 485             }
 486
 487             ast::ExprMatch(ref discr, ref arms, _) => {
 488                 let discr_cmt = return_if_err!(self.mc.cat_expr(&**discr));
 489                 self.borrow_expr(&**discr, ty::ReEmpty, ty::ImmBorrow, MatchDiscriminant);
 490
 491                 // treatment of the discriminant is handled while walking the arms.
 492                 for arm in arms.iter() {
 493                     let mode = self.arm_move_mode(discr_cmt.clone(), arm);
 494                     let mode = mode.match_mode();
 495                     self.walk_arm(discr_cmt.clone(), arm, mode);
 496                 }
 497             }
 498
 499             ast::ExprVec(ref exprs) => {
 500                 self.consume_exprs(exprs);
 501             }
 502
 503             ast::ExprAddrOf(m, ref base) => {   // &base
 504                 // make sure that the thing we are pointing out stays valid
 505                 // for the lifetime `scope_r` of the resulting ptr:
 506                 let expr_ty = return_if_err!(self.typer.node_ty(expr.id));
 507                 let r = ty::ty_region(self.tcx(), expr.span, expr_ty);
 508                 let bk = ty::BorrowKind::from_mutbl(m);
 509                 self.borrow_expr(&**base, r, bk, AddrOf);
 510             }
 511
 512             ast::ExprInlineAsm(ref ia) => {
 513                 for &(_, ref input) in ia.inputs.iter() {
 514                     self.consume_expr(&**input);
 515                 }
 516
 517                 for &(_, ref output, is_rw) in ia.outputs.iter() {
 518                     self.mutate_expr(expr, &**output,
 519                                            if is_rw { WriteAndRead } else { JustWrite });
 520                 }
 521             }
 522
 523             ast::ExprBreak(..) |
 524             ast::ExprAgain(..) |
 525             ast::ExprLit(..) => {}
 526
 527             ast::ExprLoop(ref blk, _) => {
 528                 self.walk_block(&**blk);
 529             }
 530
 531             ast::ExprWhile(ref cond_expr, ref blk, _) => {
 532                 self.consume_expr(&**cond_expr);
 533                 self.walk_block(&**blk);
 534             }
 535
 536             ast::ExprWhileLet(..) => {
 537                 self.tcx().sess.span_bug(expr.span, "non-desugared ExprWhileLet");
 538             }
 539
 540             ast::ExprForLoop(ref pat, ref head, ref blk, _) => {
 541                 // The pattern lives as long as the block.
 542                 debug!("walk_expr for loop case: blk id={}", blk.id);
 543                 self.consume_expr(&**head);
 544
 545                 // Fetch the type of the value that the iteration yields to
 546                 // produce the pattern's categorized mutable type.
 547                 let pattern_type = return_if_err!(self.typer.node_ty(pat.id));
 548                 let blk_scope = region::CodeExtent::from_node_id(blk.id);
 549                 let pat_cmt = self.mc.cat_rvalue(pat.id,
 550                                                  pat.span,
 551                                                  ty::ReScope(blk_scope),
 552                                                  pattern_type);
 553                 self.walk_irrefutable_pat(pat_cmt, &**pat);
 554
 555                 self.walk_block(&**blk);
 556             }
 557
 558             ast::ExprUnary(op, ref lhs) => {
 559                 let pass_args = if ast_util::is_by_value_unop(op) {
 560                     PassArgs::ByValue
 561                 } else {
 562                     PassArgs::ByRef
 563                 };
 564
 565                 if !self.walk_overloaded_operator(expr, &**lhs, Vec::new(), pass_args) {
 566                     self.consume_expr(&**lhs);
 567                 }
 568             }
 569
 570             ast::ExprBinary(op, ref lhs, ref rhs) => {
 571                 let pass_args = if ast_util::is_by_value_binop(op) {
 572                     PassArgs::ByValue
 573                 } else {
 574                     PassArgs::ByRef
 575                 };
 576
 577                 if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs], pass_args) {
 578                     self.consume_expr(&**lhs);
 579                     self.consume_expr(&**rhs);
 580                 }
 581             }
 582
 583             ast::ExprBlock(ref blk) => {
 584                 self.walk_block(&**blk);
 585             }
 586
 587             ast::ExprRet(ref opt_expr) => {
 588                 for expr in opt_expr.iter() {
 589                     self.consume_expr(&**expr);
 590                 }
 591             }
 592
 593             ast::ExprAssign(ref lhs, ref rhs) => {
 594                 self.mutate_expr(expr, &**lhs, JustWrite);
 595                 self.consume_expr(&**rhs);
 596             }
 597
 598             ast::ExprCast(ref base, _) => {
 599                 self.consume_expr(&**base);
 600             }
 601
 602             ast::ExprAssignOp(_, ref lhs, ref rhs) => {
 603                 // This will have to change if/when we support
 604                 // overloaded operators for `+=` and so forth.
 605                 self.mutate_expr(expr, &**lhs, WriteAndRead);
 606                 self.consume_expr(&**rhs);
 607             }
 608
 609             ast::ExprRepeat(ref base, ref count) => {
 610                 self.consume_expr(&**base);
 611                 self.consume_expr(&**count);
 612             }
 613
 614             ast::ExprClosure(..) => {
 615                 self.walk_captures(expr)
 616             }
 617
 618             ast::ExprBox(ref place, ref base) => {
 619                 match *place {
 620                     Some(ref place) => self.consume_expr(&**place),
 621                     None => {}
 622                 }
 623                 self.consume_expr(&**base);
 624             }
 625
 626             ast::ExprMac(..) => {
 627                 self.tcx().sess.span_bug(
 628                     expr.span,
 629                     "macro expression remains after expansion");
 630             }
 631         }
 632     }
 633
 634     fn walk_callee(&mut self, call: &ast::Expr, callee: &ast::Expr) {
 635         let callee_ty = return_if_err!(self.typer.expr_ty_adjusted(callee));
 636         debug!("walk_callee: callee={} callee_ty={}",
 637                callee.repr(self.tcx()), callee_ty.repr(self.tcx()));
 638         let call_scope = region::CodeExtent::from_node_id(call.id);
 639         match callee_ty.sty {
 640             ty::ty_bare_fn(..) => {
 641                 self.consume_expr(callee);
 642             }
 643             ty::ty_err => { }
 644             _ => {
 645                 let overloaded_call_type =
 646                     match self.typer.node_method_origin(MethodCall::expr(call.id)) {
 647                         Some(method_origin) => {
 648                             OverloadedCallType::from_method_origin(
 649                                 self.tcx(),
 650                                 &method_origin)
 651                         }
 652                         None => {
 653                             self.tcx().sess.span_bug(
 654                                 callee.span,
 655                                 format!("unexpected callee type {}",
 656                                         callee_ty.repr(self.tcx())).as_slice())
 657                         }
 658                     };
 659                 match overloaded_call_type {
 660                     FnMutOverloadedCall => {
 661                         self.borrow_expr(callee,
 662                                          ty::ReScope(call_scope),
 663                                          ty::MutBorrow,
 664                                          ClosureInvocation);
 665                     }
 666                     FnOverloadedCall => {
 667                         self.borrow_expr(callee,
 668                                          ty::ReScope(call_scope),
 669                                          ty::ImmBorrow,
 670                                          ClosureInvocation);
 671                     }
 672                     FnOnceOverloadedCall => self.consume_expr(callee),
 673                 }
 674             }
 675         }
 676     }
 677
 678     fn walk_stmt(&mut self, stmt: &ast::Stmt) {
 679         match stmt.node {
 680             ast::StmtDecl(ref decl, _) => {
 681                 match decl.node {
 682                     ast::DeclLocal(ref local) => {
 683                         self.walk_local(&**local);
 684                     }
 685
 686                     ast::DeclItem(_) => {
 687                         // we don't visit nested items in this visitor,
 688                         // only the fn body we were given.
 689                     }
 690                 }
 691             }
 692
 693             ast::StmtExpr(ref expr, _) |
 694             ast::StmtSemi(ref expr, _) => {
 695                 self.consume_expr(&**expr);
 696             }
 697
 698             ast::StmtMac(..) => {
 699                 self.tcx().sess.span_bug(stmt.span, "unexpanded stmt macro");
 700             }
 701         }
 702     }
 703
 704     fn walk_local(&mut self, local: &ast::Local) {
 705         match local.init {
 706             None => {
 707                 let delegate = &mut self.delegate;
 708                 pat_util::pat_bindings(&self.typer.tcx().def_map, &*local.pat,
 709                                        |_, id, span, _| {
 710                     delegate.decl_without_init(id, span);
 711                 })
 712             }
 713
 714             Some(ref expr) => {
 715                 // Variable declarations with
 716                 // initializers are considered
 717                 // "assigns", which is handled by
 718                 // `walk_pat`:
 719                 self.walk_expr(&**expr);
 720                 let init_cmt = return_if_err!(self.mc.cat_expr(&**expr));
 721                 self.walk_irrefutable_pat(init_cmt, &*local.pat);
 722             }
 723         }
 724     }
 725
 726     /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
 727     /// depending on its type.
 728     fn walk_block(&mut self, blk: &ast::Block) {
 729         debug!("walk_block(blk.id={})", blk.id);
 730
 731         for stmt in blk.stmts.iter() {
 732             self.walk_stmt(&**stmt);
 733         }
 734
 735         for tail_expr in blk.expr.iter() {
 736             self.consume_expr(&**tail_expr);
 737         }
 738     }
 739
 740     fn walk_struct_expr(&mut self,
 741                         _expr: &ast::Expr,
 742                         fields: &Vec<ast::Field>,
 743                         opt_with: &Option<P<ast::Expr>>) {
 744         // Consume the expressions supplying values for each field.
 745         for field in fields.iter() {
 746             self.consume_expr(&*field.expr);
 747         }
 748
 749         let with_expr = match *opt_with {
 750             Some(ref w) => &**w,
 751             None => { return; }
 752         };
 753
 754         let with_cmt = return_if_err!(self.mc.cat_expr(&*with_expr));
 755
 756         // Select just those fields of the `with`
 757         // expression that will actually be used
 758         let with_fields = match with_cmt.ty.sty {
 759             ty::ty_struct(did, substs) => {
 760                 ty::struct_fields(self.tcx(), did, substs)
 761             }
 762             _ => {
 763                 // the base expression should always evaluate to a
 764                 // struct; however, when EUV is run during typeck, it
 765                 // may not. This will generate an error earlier in typeck,
 766                 // so we can just ignore it.
 767                 if !self.tcx().sess.has_errors() {
 768                     self.tcx().sess.span_bug(
 769                         with_expr.span,
 770                         "with expression doesn't evaluate to a struct");
 771                 }
 772                 assert!(self.tcx().sess.has_errors());
 773                 vec!()
 774             }
 775         };
 776
 777         // Consume those fields of the with expression that are needed.
 778         for with_field in with_fields.iter() {
 779             if !contains_field_named(with_field, fields) {
 780                 let cmt_field = self.mc.cat_field(&*with_expr,
 781                                                   with_cmt.clone(),
 782                                                   with_field.name,
 783                                                   with_field.mt.ty);
 784                 self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
 785             }
 786         }
 787
 788         // walk the with expression so that complex expressions
 789         // are properly handled.
 790         self.walk_expr(with_expr);
 791
 792         fn contains_field_named(field: &ty::field,
 793                                 fields: &Vec<ast::Field>)
 794                                 -> bool
 795         {
 796             fields.iter().any(
 797                 |f| f.ident.node.name == field.name)
 798         }
 799     }
 800
 801     // Invoke the appropriate delegate calls for anything that gets
 802     // consumed or borrowed as part of the automatic adjustment
 803     // process.
 804     fn walk_adjustment(&mut self, expr: &ast::Expr) {
 805         let typer = self.typer;
 806         match typer.adjustments().borrow().get(&expr.id) {
 807             None => { }
 808             Some(adjustment) => {
 809                 match *adjustment {
 810                     ty::AdjustReifyFnPointer(..) => {
 811                         // Creating a closure/fn-pointer consumes the
 812                         // input and stores it into the resulting
 813                         // rvalue.
 814                         debug!("walk_adjustment(AutoAddEnv|AdjustReifyFnPointer)");
 815                         let cmt_unadjusted =
 816                             return_if_err!(self.mc.cat_expr_unadjusted(expr));
 817                         self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
 818                     }
 819                     ty::AdjustDerefRef(ty::AutoDerefRef {
 820                         autoref: ref opt_autoref,
 821                         autoderefs: n
 822                     }) => {
 823                         self.walk_autoderefs(expr, n);
 824
 825                         match *opt_autoref {
 826                             None => { }
 827                             Some(ref r) => {
 828                                 self.walk_autoref(expr, r, n);
 829                             }
 830                         }
 831                     }
 832                 }
 833             }
 834         }
 835     }
 836
 837     /// Autoderefs for overloaded Deref calls in fact reference their receiver. That is, if we have
 838     /// `(*x)` where `x` is of type `Rc<T>`, then this in fact is equivalent to `x.deref()`. Since
 839     /// `deref()` is declared with `&self`, this is an autoref of `x`.
 840     fn walk_autoderefs(&mut self,
 841                        expr: &ast::Expr,
 842                        autoderefs: uint) {
 843         debug!("walk_autoderefs expr={} autoderefs={}", expr.repr(self.tcx()), autoderefs);
 844
 845         for i in range(0, autoderefs) {
 846             let deref_id = ty::MethodCall::autoderef(expr.id, i);
 847             match self.typer.node_method_ty(deref_id) {
 848                 None => {}
 849                 Some(method_ty) => {
 850                     let cmt = return_if_err!(self.mc.cat_expr_autoderefd(expr, i));
 851
 852                     // the method call infrastructure should have
 853                     // replaced all late-bound regions with variables:
 854                     let self_ty = ty::ty_fn_sig(method_ty).input(0);
 855                     let self_ty = ty::assert_no_late_bound_regions(self.tcx(), &self_ty);
 856
 857                     let (m, r) = match self_ty.sty {
 858                         ty::ty_rptr(r, ref m) => (m.mutbl, r),
 859                         _ => self.tcx().sess.span_bug(expr.span,
 860                                 format!("bad overloaded deref type {}",
 861                                     method_ty.repr(self.tcx())).index(&FullRange))
 862                     };
 863                     let bk = ty::BorrowKind::from_mutbl(m);
 864                     self.delegate.borrow(expr.id, expr.span, cmt,
 865                                          *r, bk, AutoRef);
 866                 }
 867             }
 868         }
 869     }
 870
 871     fn walk_autoref(&mut self,
 872                     expr: &ast::Expr,
 873                     autoref: &ty::AutoRef,
 874                     n: uint) {
 875         debug!("walk_autoref expr={}", expr.repr(self.tcx()));
 876
 877         // Match for unique trait coercions first, since we don't need the
 878         // call to cat_expr_autoderefd.
 879         match *autoref {
 880             ty::AutoUnsizeUniq(ty::UnsizeVtable(..)) |
 881             ty::AutoUnsize(ty::UnsizeVtable(..)) => {
 882                 assert!(n == 1, format!("Expected exactly 1 deref with Uniq \
 883                                          AutoRefs, found: {}", n));
 884                 let cmt_unadjusted =
 885                     return_if_err!(self.mc.cat_expr_unadjusted(expr));
 886                 self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
 887                 return;
 888             }
 889             _ => {}
 890         }
 891
 892         let cmt_derefd = return_if_err!(
 893             self.mc.cat_expr_autoderefd(expr, n));
 894         debug!("walk_adjustment: cmt_derefd={}",
 895                cmt_derefd.repr(self.tcx()));
 896
 897         match *autoref {
 898             ty::AutoPtr(r, m, _) => {
 899                 self.delegate.borrow(expr.id,
 900                                      expr.span,
 901                                      cmt_derefd,
 902                                      r,
 903                                      ty::BorrowKind::from_mutbl(m),
 904                                      AutoRef);
 905             }
 906             ty::AutoUnsizeUniq(_) | ty::AutoUnsize(_) | ty::AutoUnsafe(..) => {}
 907         }
 908     }
 909
 910     fn walk_overloaded_operator(&mut self,
 911                                 expr: &ast::Expr,
 912                                 receiver: &ast::Expr,
 913                                 rhs: Vec<&ast::Expr>,
 914                                 pass_args: PassArgs)
 915                                 -> bool
 916     {
 917         if !self.typer.is_method_call(expr.id) {
 918             return false;
 919         }
 920
 921         match pass_args {
 922             PassArgs::ByValue => {
 923                 self.consume_expr(receiver);
 924                 for &arg in rhs.iter() {
 925                     self.consume_expr(arg);
 926                 }
 927
 928                 return true;
 929             },
 930             PassArgs::ByRef => {},
 931         }
 932
 933         self.walk_expr(receiver);
 934
 935         // Arguments (but not receivers) to overloaded operator
 936         // methods are implicitly autoref'd which sadly does not use
 937         // adjustments, so we must hardcode the borrow here.
 938
 939         let r = ty::ReScope(region::CodeExtent::from_node_id(expr.id));
 940         let bk = ty::ImmBorrow;
 941
 942         for &arg in rhs.iter() {
 943             self.borrow_expr(arg, r, bk, OverloadedOperator);
 944         }
 945         return true;
 946     }
 947
 948     fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &ast::Arm) -> TrackMatchMode<Span> {
 949         let mut mode = Unknown;
 950         for pat in arm.pats.iter() {
 951             self.determine_pat_move_mode(discr_cmt.clone(), &**pat, &mut mode);
 952         }
 953         mode
 954     }
 955
 956     fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &ast::Arm, mode: MatchMode) {
 957         for pat in arm.pats.iter() {
 958             self.walk_pat(discr_cmt.clone(), &**pat, mode);
 959         }
 960
 961         for guard in arm.guard.iter() {
 962             self.consume_expr(&**guard);
 963         }
 964
 965         self.consume_expr(&*arm.body);
 966     }
 967
 968     /// Walks an pat that occurs in isolation (i.e. top-level of fn
 969     /// arg or let binding.  *Not* a match arm or nested pat.)
 970     fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &ast::Pat) {
 971         let mut mode = Unknown;
 972         self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
 973         let mode = mode.match_mode();
 974         self.walk_pat(cmt_discr, pat, mode);
 975     }
 976
 977     /// Identifies any bindings within `pat` and accumulates within
 978     /// `mode` whether the overall pattern/match structure is a move,
 979     /// copy, or borrow.
 980     fn determine_pat_move_mode(&mut self,
 981                                cmt_discr: mc::cmt<'tcx>,
 982                                pat: &ast::Pat,
 983                                mode: &mut TrackMatchMode<Span>) {
 984         debug!("determine_pat_move_mode cmt_discr={} pat={}", cmt_discr.repr(self.tcx()),
 985                pat.repr(self.tcx()));
 986         return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |_mc, cmt_pat, pat| {
 987             let tcx = self.tcx();
 988             let def_map = &self.tcx().def_map;
 989             if pat_util::pat_is_binding(def_map, pat) {
 990                 match pat.node {
 991                     ast::PatIdent(ast::BindByRef(_), _, _) =>
 992                         mode.lub(BorrowingMatch),
 993                     ast::PatIdent(ast::BindByValue(_), _, _) => {
 994                         match copy_or_move(self.typer, &cmt_pat, PatBindingMove) {
 995                             Copy => mode.lub(CopyingMatch),
 996                             Move(_) => mode.lub(MovingMatch),
 997                         }
 998                     }
 999                     _ => {
1000                         tcx.sess.span_bug(
1001                             pat.span,
1002                             "binding pattern not an identifier");
1003                     }
1004                 }
1005             }
1006         }));
1007     }
1008
1009     /// The core driver for walking a pattern; `match_mode` must be
1010     /// established up front, e.g. via `determine_pat_move_mode` (see
1011     /// also `walk_irrefutable_pat` for patterns that stand alone).
1012     fn walk_pat(&mut self,
1013                 cmt_discr: mc::cmt<'tcx>,
1014                 pat: &ast::Pat,
1015                 match_mode: MatchMode) {
1016         debug!("walk_pat cmt_discr={} pat={}", cmt_discr.repr(self.tcx()),
1017                pat.repr(self.tcx()));
1018
1019         let mc = &self.mc;
1020         let typer = self.typer;
1021         let def_map = &self.tcx().def_map;
1022         let delegate = &mut self.delegate;
1023         return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |mc, cmt_pat, pat| {
1024             if pat_util::pat_is_binding(def_map, pat) {
1025                 let tcx = typer.tcx();
1026
1027                 debug!("binding cmt_pat={} pat={} match_mode={:?}",
1028                        cmt_pat.repr(tcx),
1029                        pat.repr(tcx),
1030                        match_mode);
1031
1032                 // pat_ty: the type of the binding being produced.
1033                 let pat_ty = return_if_err!(typer.node_ty(pat.id));
1034
1035                 // Each match binding is effectively an assignment to the
1036                 // binding being produced.
1037                 let def = def_map.borrow()[pat.id].clone();
1038                 match mc.cat_def(pat.id, pat.span, pat_ty, def) {
1039                     Ok(binding_cmt) => {
1040                         delegate.mutate(pat.id, pat.span, binding_cmt, Init);
1041                     }
1042                     Err(_) => { }
1043                 }
1044
1045                 // It is also a borrow or copy/move of the value being matched.
1046                 match pat.node {
1047                     ast::PatIdent(ast::BindByRef(m), _, _) => {
1048                         let (r, bk) = {
1049                             (ty::ty_region(tcx, pat.span, pat_ty),
1050                              ty::BorrowKind::from_mutbl(m))
1051                         };
1052                         delegate.borrow(pat.id, pat.span, cmt_pat,
1053                                              r, bk, RefBinding);
1054                     }
1055                     ast::PatIdent(ast::BindByValue(_), _, _) => {
1056                         let mode = copy_or_move(typer, &cmt_pat, PatBindingMove);
1057                         debug!("walk_pat binding consuming pat");
1058                         delegate.consume_pat(pat, cmt_pat, mode);
1059                     }
1060                     _ => {
1061                         tcx.sess.span_bug(
1062                             pat.span,
1063                             "binding pattern not an identifier");
1064                     }
1065                 }
1066             } else {
1067                 match pat.node {
1068                     ast::PatVec(_, Some(ref slice_pat), _) => {
1069                         // The `slice_pat` here creates a slice into
1070                         // the original vector.  This is effectively a
1071                         // borrow of the elements of the vector being
1072                         // matched.
1073
1074                         let (slice_cmt, slice_mutbl, slice_r) =
1075                             return_if_err!(mc.cat_slice_pattern(cmt_pat, &**slice_pat));
1076
1077                         // Note: We declare here that the borrow
1078                         // occurs upon entering the `[...]`
1079                         // pattern. This implies that something like
1080                         // `[a; b]` where `a` is a move is illegal,
1081                         // because the borrow is already in effect.
1082                         // In fact such a move would be safe-ish, but
1083                         // it effectively *requires* that we use the
1084                         // nulling out semantics to indicate when a
1085                         // value has been moved, which we are trying
1086                         // to move away from.  Otherwise, how can we
1087                         // indicate that the first element in the
1088                         // vector has been moved?  Eventually, we
1089                         // could perhaps modify this rule to permit
1090                         // `[..a, b]` where `b` is a move, because in
1091                         // that case we can adjust the length of the
1092                         // original vec accordingly, but we'd have to
1093                         // make trans do the right thing, and it would
1094                         // only work for `~` vectors. It seems simpler
1095                         // to just require that people call
1096                         // `vec.pop()` or `vec.unshift()`.
1097                         let slice_bk = ty::BorrowKind::from_mutbl(slice_mutbl);
1098                         delegate.borrow(pat.id, pat.span,
1099                                         slice_cmt, slice_r,
1100                                         slice_bk, RefBinding);
1101                     }
1102                     _ => { }
1103                 }
1104             }
1105         }));
1106
1107         // Do a second pass over the pattern, calling `matched_pat` on
1108         // the interior nodes (enum variants and structs), as opposed
1109         // to the above loop's visit of than the bindings that form
1110         // the leaves of the pattern tree structure.
1111         return_if_err!(mc.cat_pattern(cmt_discr, pat, |mc, cmt_pat, pat| {
1112             let def_map = def_map.borrow();
1113             let tcx = typer.tcx();
1114
1115             match pat.node {
1116                 ast::PatEnum(_, _) | ast::PatIdent(_, _, None) | ast::PatStruct(..) => {
1117                     match def_map.get(&pat.id) {
1118                         None => {
1119                             // no definition found: pat is not a
1120                             // struct or enum pattern.
1121                         }
1122
1123                         Some(&def::DefVariant(enum_did, variant_did, _is_struct)) => {
1124                             let downcast_cmt =
1125                                 if ty::enum_is_univariant(tcx, enum_did) {
1126                                     cmt_pat
1127                                 } else {
1128                                     let cmt_pat_ty = cmt_pat.ty;
1129                                     mc.cat_downcast(pat, cmt_pat, cmt_pat_ty, variant_did)
1130                                 };
1131
1132                             debug!("variant downcast_cmt={} pat={}",
1133                                    downcast_cmt.repr(tcx),
1134                                    pat.repr(tcx));
1135
1136                             delegate.matched_pat(pat, downcast_cmt, match_mode);
1137                         }
1138
1139                         Some(&def::DefStruct(..)) | Some(&def::DefTy(_, false)) => {
1140                             // A struct (in either the value or type
1141                             // namespace; we encounter the former on
1142                             // e.g. patterns for unit structs).
1143
1144                             debug!("struct cmt_pat={} pat={}",
1145                                    cmt_pat.repr(tcx),
1146                                    pat.repr(tcx));
1147
1148                             delegate.matched_pat(pat, cmt_pat, match_mode);
1149                         }
1150
1151                         Some(&def::DefConst(..)) |
1152                         Some(&def::DefLocal(..)) => {
1153                             // This is a leaf (i.e. identifier binding
1154                             // or constant value to match); thus no
1155                             // `matched_pat` call.
1156                         }
1157
1158                         Some(def @ &def::DefTy(_, true)) => {
1159                             // An enum's type -- should never be in a
1160                             // pattern.
1161
1162                             if !tcx.sess.has_errors() {
1163                                 let msg = format!("Pattern has unexpected type: {:?} and type {}",
1164                                                   def,
1165                                                   cmt_pat.ty.repr(tcx));
1166                                 tcx.sess.span_bug(pat.span, msg.as_slice())
1167                             }
1168                         }
1169
1170                         Some(def) => {
1171                             // Remaining cases are e.g. DefFn, to
1172                             // which identifiers within patterns
1173                             // should not resolve. However, we do
1174                             // encouter this when using the
1175                             // expr-use-visitor during typeck. So just
1176                             // ignore it, an error should have been
1177                             // reported.
1178
1179                             if !tcx.sess.has_errors() {
1180                                 let msg = format!("Pattern has unexpected def: {:?} and type {}",
1181                                                   def,
1182                                                   cmt_pat.ty.repr(tcx));
1183                                 tcx.sess.span_bug(pat.span, msg.index(&FullRange))
1184                             }
1185                         }
1186                     }
1187                 }
1188
1189                 ast::PatIdent(_, _, Some(_)) => {
1190                     // Do nothing; this is a binding (not a enum
1191                     // variant or struct), and the cat_pattern call
1192                     // will visit the substructure recursively.
1193                 }
1194
1195                 ast::PatWild(_) | ast::PatTup(..) | ast::PatBox(..) |
1196                 ast::PatRegion(..) | ast::PatLit(..) | ast::PatRange(..) |
1197                 ast::PatVec(..) | ast::PatMac(..) => {
1198                     // Similarly, each of these cases does not
1199                     // correspond to a enum variant or struct, so we
1200                     // do not do any `matched_pat` calls for these
1201                     // cases either.
1202                 }
1203             }
1204         }));
1205     }
1206
1207     fn walk_captures(&mut self, closure_expr: &ast::Expr) {
1208         debug!("walk_captures({})", closure_expr.repr(self.tcx()));
1209
1210         ty::with_freevars(self.tcx(), closure_expr.id, |freevars| {
1211             match self.tcx().capture_mode(closure_expr.id) {
1212                 ast::CaptureByRef => {
1213                     self.walk_by_ref_captures(closure_expr, freevars);
1214                 }
1215                 ast::CaptureByValue => {
1216                     self.walk_by_value_captures(closure_expr, freevars);
1217                 }
1218             }
1219         });
1220     }
1221
1222     fn walk_by_ref_captures(&mut self,
1223                             closure_expr: &ast::Expr,
1224                             freevars: &[ty::Freevar]) {
1225         for freevar in freevars.iter() {
1226             let id_var = freevar.def.def_id().node;
1227             let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
1228                                                                closure_expr.span,
1229                                                                freevar.def));
1230
1231             // Lookup the kind of borrow the callee requires, as
1232             // inferred by regionbk
1233             let upvar_id = ty::UpvarId { var_id: id_var,
1234                                          closure_expr_id: closure_expr.id };
1235             let upvar_borrow = self.typer.upvar_borrow(upvar_id).unwrap();
1236
1237             self.delegate.borrow(closure_expr.id,
1238                                  closure_expr.span,
1239                                  cmt_var,
1240                                  upvar_borrow.region,
1241                                  upvar_borrow.kind,
1242                                  ClosureCapture(freevar.span));
1243         }
1244     }
1245
1246     fn walk_by_value_captures(&mut self,
1247                               closure_expr: &ast::Expr,
1248                               freevars: &[ty::Freevar]) {
1249         for freevar in freevars.iter() {
1250             let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
1251                                                                closure_expr.span,
1252                                                                freevar.def));
1253             let mode = copy_or_move(self.typer, &cmt_var, CaptureMove);
1254             self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
1255         }
1256     }
1257
1258     fn cat_captured_var(&mut self,
1259                         closure_id: ast::NodeId,
1260                         closure_span: Span,
1261                         upvar_def: def::Def)
1262                         -> mc::McResult<mc::cmt<'tcx>> {
1263         // Create the cmt for the variable being borrowed, from the
1264         // caller's perspective
1265         let var_id = upvar_def.def_id().node;
1266         let var_ty = try!(self.typer.node_ty(var_id));
1267         self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
1268     }
1269 }
1270
1271 fn copy_or_move<'tcx>(typer: &mc::Typer<'tcx>,
1272                       cmt: &mc::cmt<'tcx>,
1273                       move_reason: MoveReason)
1274                       -> ConsumeMode
1275 {
1276     if typer.type_moves_by_default(cmt.span, cmt.ty) {
1277         Move(move_reason)
1278     } else {
1279         Copy
1280     }
1281 }